var expect=require('chai').expect;

var timeout=(ms,cb)=>{
    setTimeout(()=>{
        if(Math.random()<0.5){
            cb(null,'Success');
        }else{
            cb(new Error('404'));
        }
    },ms);
}

describe('异步',()=>{
    it('without error',(done)=>{
        timeout(200,done);
    });
});